To ventilate, and to deliver hot or cold air into, the cabin of a motor vehicle, a ventilation device is connected to an air conditioning and/or heating system to supply air to the motor vehicle cabin. As illustrated in FIGS. 1, 1b, and 1c, the ventilation device 1 comprises a casing 6, an electric motor 4, and a blower impeller 5, the latter having vanes 5a and a hub 5b and being driven by this motor. The casing 6, which is usually shaped like a spiral cylinder, comprises a peripheral wall 6a and two open ends 6b, 6c, the first open end 6b acting as the air inlet of the ventilation device 1 and the second open end 6c allowing the blower impeller 5 to be inserted into the internal volume of the casing 6. Also, this casing 6 defines a main air channel 7 carrying the air flow produced by the blower impeller to the air-conditioning and/or heating system. This blower impeller is connected to the electric motor 4 and is therefore held in the casing 6 by an attachment, in the second opening 6c, of a motor cradle 9 casing the electric motor 4. In this way, part of said motor housed in the bowl 5c of the impeller 5 is inside the casing 6, while the other part of the motor 4 is inside the motor cradle 9. The blower impeller 5 is driven by the electric motor 4, so that this air flow is produced by the operation of said motor. Thus, whenever the air conditioning and/or heating system is on, the electric motor 4 is running and generating heat. It is therefore vital to cool this motor to prevent it being damaged by prolonged use of the air conditioning and/or heating system.
To cool the electric motor when it is running, one approach has been to divert some of the air flow generated by the blower impeller for the air conditioning and/or heating system, so that the motor is cooled by an air flow over it. To divert some of the air flow, a secondary channel 8 is added. This secondary channel 8 comprises an air flow inlet 11 and an air flow outlet 12. The air flow inlet 11 is located in a side wall 7c of the main channel 7. The air flow outlet 12 corresponds to the air flow inlet of a duct 9a formed in the motor cradle 9. This duct is also shaped in such a way that it takes the air flow coming from the secondary channel and conveys it to the electric motor.
However, this method of cooling the electric motor has one great drawback in that the diverted air flow may be damp. This dampness may be due to weather conditions (rain, humid external air) or to water being forced in, for example during pressure-washing of the engine compartment or when the vehicle's bodywork is being washed. On these occasions, water may get into the ventilation device through its air inlet. The electric motor may therefore come into contact with water, exposing it to a serious risk of damage.
Since manufacturers' standards are becoming more and more demanding in the automotive field, for reasons of safety and durability, it is desirable to reduce the presence of water in the air flow used to cool the electric motor.
The problem is therefore how to reduce the amount of water transported by the air flow through the secondary channel and thus avoid having the electric motor coming into contact with a liquid or with over-humid air when it is running.
The applicant's invention solves this problem with a ventilation device comprising a casing suitable for channeling at least one air flow set up by a blower impeller, which casing defines a main air channel carrying a main air flow, and a secondary air channel designed to carry a secondary air flow to a motor in order to cool it, said secondary channel having on the one hand an inlet located in a wall of the main channel and on the other hand an outlet located in a plane containing an end of the casing through which the impeller is inserted; which device is characterized in that the secondary channel has a means designed to cause the secondary air flow to change direction at least twice as it travels along said secondary channel.
The provision of a means for diverting the air flow into the secondary channel prevents water reaching the outlet, because the various changes of direction imposed on the air flow in the secondary channel force the water droplets transported by this air flow to remain in a part of the secondary channel. The particular way in which the means is arranged prevents the water from getting as far as the motor cradle duct and damaging the motor.
In one particular embodiment, said means comprises at least one wall dividing said secondary channel into at least two sub-channels. The creation of two sub-channels makes it possible to impose a special route on the air flowing through the sub-channels. Moreover, one of the two sub-channels performs two functions—collecting water droplets transported in the air flow, and removing these collected droplets.
Advantageously, one wall of the second sub-channel doubles as the wall of the volute tongue of the casing. Sitting the second sub-channel here allows an unused region of the casing to be occupied. Placing the second sub-channel in the volute tongue therefore makes the casing easy to fabricate and cheap to produce. Further, this sub-channel is placed in this region for fluid-flow reasons, to avoid head losses.
Advantageously, the means also includes the inlet and the outlet, these being arranged at one end of the secondary channel, and it includes the wall which contains an opening between the two sub-channels, said opening being arranged at the opposite end from the end where the inlet and outlet are located. The particular arrangement of the inlet and outlet with respect to the opening makes it possible to form a baffle which will force the air flow to change direction at least twice before it reaches the outlet. This baffle thus prevents water reaching the outlet.
Advantageously, the inlet of the secondary channel is defined by a rim, the opening is defined by an edge, and the rim is located at a height less than the height of the edge in relation to the total height of the secondary channel. This arrangement of the inlet relative to the opening ensures that air flowing through the secondary channel cannot travel along the sub-channel comprising the outlet without changing direction.
Advantageously, the wall forming the sub-channels and the wall of the casing containing the inlet are perpendicular to each other. The arrangement of these two walls again simplifies the production of the secondary channel.
Advantageously, the casing comprises two half-shells engaging at a parting line, at least one of which two half-shells includes, projecting from the parting line, a part whose free end at least partially defines the inlet.
Advantageously, said casing comprises two half-shells engaging at a parting line, at least one of which two half-shells includes, projecting from the parting line, a part whose free end at least partially defines the opening. This two half-shell structure makes it easy to mold the sub-channels. This means that the manufacturing cost does not have to be increased because an extra part can be inserted to form both the secondary channel and the wall dividing it into two sub-channels.
Advantageously, a heating and/or air conditioning system comprises a ventilation device that incorporates at least one of the features indicated above.